LETTER : Speedy control of traffic pollution

Sir: Your article on measures to control vehicle air pollution ("Air quality set to remain poor", 5 May) failed to mention one existing legal restraint which is insufficiently used in cities - speed limits.

Nearly all forms of vehicle pollution are directly proportional to the amount of fuel burnt, so the faster and more aggressively a car is driven, the worse it pollutes. If the 30mph speed limit was properly enforced, and drivers could restrain themselves from roaring away from traffic lights, there would be a useful reduction in urban pollution.

Drivers in London know they can get away with 40mph. There are too few of the recently introduced Gatso automatic radar cameras, and they seem to be set at 40mph-plus. Why not set them at 30mph? It might mean a mountain of prosecution paperwork in the short term, but in the long term we'd have cleaner air.